In an effort to provide large, wall size displays, many projection techniques have been utilized in which video information is projected on to a screen. Such systems are bulky and expensive, and do not lend themselves easily to outdoor applications such as billboards, signage or where large flat screens are required. Moreover, these techniques are not well adopted to wide screen TV or theatrical applications even though there have been many attempts to do so.
There are presently efforts under way to use large scale integrated circuit technology to extend the solid state display out to much larger dimensions. This is done primarily through the use of active semiconductor elements placed in an X/Y addressable array. However, these active matrix TV techniques are not well adapted to large screen displays over more than tens of inches due to registration problems, poor yields and the requirement for the maintenance of strict manufacturing tolerances. As a result, as photolithography is applied at larger scales, fundamental problems arise which drastically impact the yield and reliability of the resulting devices. As the size and complexity of the circuits increase, this multiplicative effect can drive the yield and reliability of the circuits to unacceptably low numbers.
A second problem with applying photolithography to large screen displays is an incompatibility of scale. Producing active components requires registration of multiple masks to dimensions on the order of a micron. Unfortunately, for a 19 inch TV, a 19 inch substrate will deform due to thermal expansion so that it is impossible to properly register the masks. A technically intensive solution to this problem has been devised by MRS Technology of Burlington, Mass. in which the required TV aperture is divided into sub-apertures which are imaged separately. As the imaging system steps from one section to another it must sense the location of the previous mask layers and properly register the next mask. Together the problems with component yield and incompatibility of scale have delayed the realization of large active-matrix flat panel displays. Thus prior art large screen displays have suffered from the problems of component yield, correlation of component failures and mask registration.
As illustrated in U.S. Pat. No. 4,136,436, and by way of further background, Texas Instruments, Inc. of Dallas, Tex., has provided concentric spherical semiconductor devices embedded in a rigid epoxy used as photovoltaic sources with the use of an electrolyte. While this technique provides pn junctions in spherical form distributed across a rigid place, it will be appreciated that this technology does not result in a display and is non-flexible, precluding use in a large size application requiring an easily erectable flexible display.